Jacoby Ellsbury

J.D. Martinez bats during the American League Division Series against the Baltimore Orioles at Comerica Park on Oct. 5, 2014. (Photo by Gregory Shamus/Getty Images)

The Detroit Tigers have agreed with outfielder J.D. Martinez on a two-year deal worth $18.5 million, avoiding arbitration with the slugger until he becomes eligible for free agency after the 2017 season.

The deal, first reported by Robert Murray of Baseball Essential and later confirmed by Chris Cotillo of MLB Daily Dish, might be the best the Tigers have on the books with their 17 players beyond the pre-arbitration phase. The length, crucially, will allow the team to wait to see whether Justin Upton exercises his opt-out clause before deciding whether to pursue a long-term contract with Martinez.

Jennifer Hammond of Fox 2 Detroit reported Martinez, whose deal is pending a passed physical, will earn $6.75 million this year and $11.75 the next. Averaged over the two seasons at $9.25 million (and even at face value), the price is higher than the $8 million Martinez sought when 2016 salary numbers were exchanged before the Jan. 15 deadline. The price tag also is more than 50 percent higher than the $6 million Detroit offered him at that time, three days before it signed Upton.

J.D. Martinez celebrates after hitting a two-run home run against the Chicago White Sox on June 25, 2015. (Photo by Duane Burleson/Getty Images)

Still, the new J.D. Martinez contract might be the Tigers’ most valuable. By giving Martinez a little more money up front and signing him for an extra year, general manager Al Avila secured one of the greatest potential bargains of 2017.

MLB Trade Rumors projected Martinez’s arbitration salary at $7.8 million after he made $3 million last season. The arbitration panel likely would have awarded him the $8 million he requested, meaning Detroit, by locking him up, essentially got him for $10.5 million next year. Considering his career trajectory and skyrocketing worth, Martinez likely would have received an even bigger arbitration payday next offseason had he stuck to a one-year deal.

Matt Swartz of MLBTR compared the Martinez case to those of Chris Davis and Jacoby Ellsbury, who got huge raises after their breakout seasons. Notably, Davis and Ellsbury both had comparatively dismal seasons immediately after and still got raises of $1.65 million and $950,000 in their final years of arbitration eligibility.

Martinez, though, has shown no signs he will falter as they did. Last season, his triple-slash line was down across the board, from .315/.358/.553 in 2014 to .282/.344/.535. But advanced statistics suggest he became a more disciplined, productive, and sustainable hitter in 2015:

Statistic

2013

2014

2015

K%

26.5

26.3

27.1

Walk%

3.2

6.3

8.1

O-Swing%

35.8

37.7

36.4

Z-Contact%

83.6

81.8

80.6

P/PA

3.78

3.9

3.96

BABIP

0.319

0.389

0.339

LD%

21.7

22.7

22.3

GB%

44.2

40.5

34.2

FB%

34.1

36.8

43.5

GB/FB

1.3

1.1

0.79

HR/FB

9.5

19.5

20.8

You’ll notice his strikeout rate was higher last season, up to 27.1 percent. But besides the increase being incremental, it’s also understandable given that Martinez is a power hitter who blasted 38 home runs. He also walked in 8.1 percent of his plate appearances, almost a third more often than he did in 2014 after barely taking bases on balls during his 2013 half-season with the Houston Astros. He made contact a little less often when he swung at pitches inside the zone, but he also swung less often at pitches outside the zone.

More often, he waited for his pitch. And he squared them up. His batting average was down, along with his BABIP, but his line drive rate stayed relatively flat. What changed most drastically from 2014 to 2015 was his ground ball to fly ball ratio, which decreased by a massive 28.2 percent. In doing so, he sacrificed his batting average somewhat (as a rule, ground balls go for hits more often than fly balls that don’t leave the ballpark).

But that sacrifice was clearly for the best. Martinez has discovered the type of hitter he is: the type that can absolutely and consistently mash baseballs with a bat. While hitting more fly balls last season, an even higher percentage of them (20.8) went for home runs. His hard-hit rate of 42.3 percent was also the best mark in the major leagues.

The improvement is no fluke. This article from June by Eno Sarris of FanGraphs demonstrates that Martinez is a thoughtful player who has made calculated changes to his swing to become more effective. Barring injury, he will be one of the league’s premier hitters for a long time—including in 2017, when the Tigers will have him in their lineup for a relative song.